I want to move my heater 15' from where it is now on the same side of my garage wall. The plumbing comes out of a sheet rock framed wall however the rest of the garage is block construction. I plan to run the cpvc lines down the block wall and insulate the hot water line. My question is can I do the same for the release valve drain? I figure I can as long as the drain line is lower than the top of the heater.

Welcome August Nine:
Your temperature and pressure relief valve should have the shortest exit possible for your safety. It is there to vent steam and scalding hot water and should be run through the wall at the water heater, down to within 4" of the ground.
Glenn

Is there any reason he can't have it discharge directly onto the garage floor?

Here in Winnipeg where most houses have their water heaters in their basements, it's not feasible to have the T&P relief valve discharge outside, so everyone just pipes them to within a few inches of the floor. Considering they rarely ever discharge, is it really necessary to pipe it through a concrete block wall?

Go to the city code site in your area and look up what requirements are in place for heaters. having a heater in a basement allows for your t&p relief to drain to the floor.. Others cities and states have different requirements for different applications and the codes are there for your safty even though it can sometimes be a pain in the rear...